What sort and how big an end mill or other milling cutter?

[NigeParticipant @nige81730]

What sort and how big a diameter milling/end milling type cutter should I be able to use in the ML4 (smaller than the ML7) considering I need to take a 30 mm diameter cut in cast iron or is the perceived 'power' of the lathe the wrong parameter to be thinking about?

[NigeParticipant @nige81730]

[John HaineParticipant @johnhaine32865]

You have answered the "how big" question haven't you? i.e. 30mm diameter. Or do you mean 30mm wide which could be taken in several passes? If you do mean diameter then I suggest a fly cutter run at lowest non-BG speed and a shallow cut. A 30mm end mill will be expensive and doing any kind of work where you are making real use of all the teeth is probably too much for milling in a light lathe. If you do use an end mill I'd suggest no bigger than 12mm/half inch.

[SillyOldDufferModerator @sillyoldduffer]

Lots of problems milling in a lathe that are overcome by taking it gently, perhaps very gently.

The main limitation of milling on my mini-lathe was insufficient rigidity in the top-slide rather than motor power. That is anything other than a light cut caused the slide and work to move, plus there's a risk of an end-mill shifting in the chuck when the going gets heavy.

I'd try a fly cutter provided there's enough travel to accommodate it. Lack of travel is the other big problem with lathe milling; smallish jobs only.

Please tell us how you get on. Before milling machines chaps did it all the time. It's a real test of ingenuity and technique. To my shame I wimped out and bought a milling machine.

Dave

Edit: I see John Haine posted while I was typing.   Yeah, wot he said!

Edited By SillyOldDuffer on 09/07/2017 12:46:44

[NigeParticipant @nige81730]

Thanks John. 30 mm wide so i can take several passes without any height changes. This question was generated by a comment from another thread where I had suggested I use a fly cutter. I thought I would explore the possibility of using some sort of milling cutter and have discovered that the bigger ones are indeed quite expensive. The fly cutter is the cheap option though probably not cheap on time.

I could use a small diameter end mill and take many passes but constantly adjusting the height of the work (I don't have a vertical slide yet) will probably take as long or longer than using the fly cutter and introduce more opportunities to get things wrong though maybe more opportunities to practice setting work up accurately as well. 

 

Edited By Nige on 09/07/2017 12:47:22

[NigeParticipant @nige81730]

Dave: Thanks; I think the cross slide on the ML4 is rigid enough and also doesn't appear to have much 'play' in it. Cross slide travel is 5 1/2 inches which is enough as long as I place the work piece correctly. I think the fly cutter is the way to go not least because it can not shift backwards in the chuck I will try and record how the job goes and share it here

Nige

[Ady1Participant @ady1]

When I did a fair bit of milling on a Myford M series I found I could cut a 12mm slot two to three times faster with a 6mm endmill compared to a 12mm endmill, and it did a better neater job.

The smaller endmills have more torque at the tip = more cutting power

The differences in diameter appear tiny but the difference in workrate can be amazing on a small machine

[MWParticipant @mw27036]

Posted by Ady1 on 09/07/2017 13:25:54:

When I did a fair bit of milling on a Myford M series I found I could cut a 12mm slot two to three times faster with a 6mm endmill compared to a 12mm endmill, and it did a better neater job.

The smaller endmills have more torque at the tip = more cutting power

The differences in diameter appear tiny but the difference in workrate can be amazing on a small machine

It's probably the same reason why many would find it easier to drill a smaller hole before drilling a much larger hole. There's simply less work for it to do.

Michael W

[Russell EberhardtParticipant @russelleberhardt48058]

Before I bought a mill, I frequently used a homemade holder that bolted into a slot on the faceplate and took a piece of round HSS as a fly cutter. That gave me anything up to about an eight inch diameter cut.

I also used end mills up to 1/2 in held in the three jaw with brass shims between it and the chuck jaws to prevent pull out.

You will have more problems with rigidity than lack of power. Make sure all gibs are nice and tight.

Russell.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Nige on 09/07/2017 12:57:03:

… I think the cross slide on the ML4 is rigid enough and also doesn't appear to have much 'play' in it.

…

Nige

Yes indeed but the booby trap is that a lathe cross-slide isn't designed to deal with milling forces. Normally the cross-side pushes a single-point tool against the work. The force on the tool is pretty much in one direction and the cross-slide is engineered to deal with it. Also, because the force is unidirectional, any slack and backlash in the system are taken up and held as the cut is applied. It's a stable arrangement that works well.

Milling applies dramatically different forces and it doesn't help that a milling cutter has much bigger cutting edges than a lathe tool. Because the tool is spinning, so is the direction of the cut. The cross-slide is forced down, right, up and left repeatedly. It is pushed hard in directions the lathe designer never took seriously. And any slack in the screws and gibs will allow enough movement to cause trouble.

The best way to get a feel for what works and what doesn't on your lathe is to try it. It's very educational!

Dave

[NigeParticipant @nige81730]

Thank you all. I might buy a small diameter end mill just to experiment with.

For say a 6 or 8 mm end mill do I need a 'special chuck' or will I get away with the three jaw chuck?

Nige

Edited By Nige on 09/07/2017 16:33:39

[SillyOldDufferModerator @sillyoldduffer]

I just used a 3-jaw.

[NigeParticipant @nige81730]

Thanks Dave

Nige

[MWParticipant @mw27036]

Posted by SillyOldDuffer on 09/07/2017 16:28:50:

Posted by Nige on 09/07/2017 12:57:03:

… I think the cross slide on the ML4 is rigid enough and also doesn't appear to have much 'play' in it.

…

Nige

Yes indeed but the booby trap is that a lathe cross-slide isn't designed to deal with milling forces. Normally the cross-side pushes a single-point tool against the work. The force on the tool is pretty much in one direction and the cross-slide is engineered to deal with it. Also, because the force is unidirectional, any slack and backlash in the system are taken up and held as the cut is applied. It's a stable arrangement that works well.

Milling applies dramatically different forces and it doesn't help that a milling cutter has much bigger cutting edges than a lathe tool. Because the tool is spinning, so is the direction of the cut. The cross-slide is forced down, right, up and left repeatedly. It is pushed hard in directions the lathe designer never took seriously. And any slack in the screws and gibs will allow enough movement to cause trouble.

The best way to get a feel for what works and what doesn't on your lathe is to try it. It's very educational!

Dave

There is really no fundamental difference in the construction of the slides between a lathe and a mill in my experience. The biggest differences appear when you get to the headstock in terms of collets and drawbars rather than a chuck, and the arrangement and movement of the slides is obviously different.

If anything, a modern lathe relying on a polyform bedway slide is more rigidly constructed than a simple vee groove simply to counteract the twisting motion Imposed on the saddle during rack feed. Probably one of the main reasons why my Clarke never had a rack and pinion feed (simply directly bolted to the feednut and handle.

(You may have seen the post on my failed experiment with a rack/pinion feed, due to the reason outlined above, though I think I may have found a clever workaround, it'll work this time I think!) 

As far as I know my mill uses vee groove slides, one thing I would agree is that with a mill it's a lot heftier than the cross slide though, as the travel tends to be far shorter on a lathe. In theory with a sensible set up there is no reason why he couldn't do milling on a lathe, I have milled a cast iron piece on the lathe before and found I could take quite a cut with it.  Just make sure those bolts are done up tight on the vise, Nigel! 

Michael W

 

Edited By Michael-w on 09/07/2017 21:04:15

[NigeParticipant @nige81730]

Thanks Michael😀 In the end I just have to get on and use what I have bearing in mind all the engineering compromises that are being stretched when you use a machine tool for purposes for which it probably wasn't intended. I am not in a position to purchase any sort of dedicated milling set up nor change my ML4 for something bigger or more robustly built. I like the definition I was given many years ago that says "an engineer is somebody who can make for 50p something that anybody else can make for a quid". I have to get on and do my best with what I have, can make or afford to buy and that is made doable by being able to seek answers from people with more experience and knowledge than I have at the moment. That's why I subscribe to MEW and why forums like this are such wonderful places 😀

[PeteParticipant @pete41194]

If your trimming that lump off your vise as shown in the other thread then bandsawing or even hacksawing off the majority of what needs to be removed first will make the job far faster and easier on the machine. With a flycutter in the lathe you will or should see the tool cutting on the backside of the cut once you get across the job far enough but it will be by a very small amount. That's quite normal and doesn't indicate a misalignment of the headstock. It's mostly caused by the cutter flexing and not taking 100% of the cut that was dialed in.

Before the influx of the much cheaper offshore benchtop mills started and with tough times for many in the UK even up into the 1960's due to the war few had the luxury of having any sort of a mill in a home shop. The very small BCA jig borers sold for almost 4 times what a then brand new Myford Super 7 was selling for. The old Model Engineer magazines show some extremely complex milling tasks all done on the only machine tool many had in the shop, there lathe. For anyone trying to do the same today I can't recommend the Workshop Practice book Milling in the Lathe highly enough.Even having a vertical mill it can still teach a lot. I have a Bridgeport clone yet still bought a large Palmgren milling attachment for the lathe. It's rare, but some jobs such as milling, drilling, boring or tapping the ends of long bars can still be done easier while using that milling attachment and the lathes headstock much like a horizontal mill. Boring between centers with the work on the lathes cross slide for work that fits is still a more accurate and better but slower method for through bores than a vertical mill is with a boring head.

[Author]

Posts